The invention relates to a mobile crane comprising a frame which, in its upper part, is provided with a main support structure and which, in its lower part and on opposite sides of the lower part of the frame, is provided with lower beam structures transverse to the main support structure, and upright legs between the main support structure and the lower beam structures; at least one wheel or wheel arrangement at both ends of the lower beam structures, i.e. in each lower corner of the crane; a trolley arranged to move along the main support structure and provided with a hoisting member; at least one hoisting mechanism; at least one rope drum arranged to be run by the hoisting mechanism; at least one rope arranged from the rope drum of the hoisting mechanism to the hoisting member for running the hoisting member.
Such yard gantry cranes for storage areas in container terminals are designed for arranging and handling containers in a container storage yard. They move along paths parallel with container rows, either on rails or rubber wheels.
Typically, the hoisting mechanism of such a crane is located in a trolley moving on top of the main support structure of the crane, in which case the masses to be moved are quite large, which has a substantial influence on the dimensioning of the support structures of the entire crane.
The known cranes on a mobile platform are susceptible to accelerations and decelerations as well as, in ports, typically, the influence of wind and stormy weather, and they are expected to be stable against falling down.
A known solution also requires demanding service and maintenance procedures to be taken into consideration in high places whereto the necessary, possibly heavy and large spare parts also have to be moved in connection with service operations.